1. Field of the Invention
The present invention relates to testing of integrated network devices such as integrated network switches configured for switching data packets between subnetworks.
2. Background Art
Local area networks use a network cable or other media to link stations on the network. Each local area network architecture uses a media access control (MAC) enabling network interface devices at each network node to access the network medium.
Switched local area networks are encountering increasing demands for higher speed connectivity, more flexible switching performance, and the ability to accommodate more complex network architectures. For example, commonly-assigned U.S. Pat. No. 5,953,335 discloses a network switch configured for switching layer 2 type Ethernet (IEEE 802.3) data packets between different network nodes; a received layer 2 type data packet may include a VLAN (virtual LAN) tagged frame according to IEEE 802.1p (802.1D) protocol that enables the network switch to perform more advanced switching operations. For example, the VLAN tag may specify another subnetwork (via a router) or a prescribed group of stations.
A particular concern in testing high-performance integrated network switches implemented on a single chip is incompatibility of existing test equipment with newer switch designs. For example, switch emulation systems are computer-based systems that execute software configured for simulating network switch operations. Hence, switch designers and testers may wish to test the switch emulation systems (simulating a network switch under design) to validate the operation and performance of the network switch.
Unfortunately, the computer-based switch emulation system may not be usable with existing network based test instruments configured for testing network devices according to IEEE 802.3 protocol. In particular, conventional test instruments, such as a packet generator or a network analyzer, may be configured for sending and receiving data across a 10BaseT or 100 BaseT interface. The switch emulation system, however, is generally unable to execute at the rate of the 10BaseT/100 BaseT interfaces of the typical test instruments. Hence, the switch emulation system, operating much slower than the 10BaseT/100 BaseT interfaces of the typical test instruments, cannot be connected to the test instruments using a normal Ethernet type connection.
There is a need for an arrangement that enables a switch emulation system, configured for emulating prescribed switch operations, to be connected to network based test equipment for evaluation of the prescribed switch operations.
These and other needs are attained by the present invention, where a test system includes a switch emulator, a network test device, and an interface converter. The switch emulator is configured for transmitting first network data on a first media independent interface based on a first interface clock, and the network test device configured for transmitting second network data on a second media independent interface based on a second interface clock. The interface converter, having inverted media independent interfaces, is configured for transferring the first and second network data between the first and second media independent interfaces, and supplying the first and second interface clocks based on an external clock generated by the switch emulator. Generation of the first and second interface clocks based on the external clock generated by the switch emulator enables the MII interfaces of the switch emulator and the network test device to be synchronized, ensuring that network data can be passed between the switch emulator and the network test device according to network protocols, even if the switch emulator is operating at relatively slow speeds.
One aspect of the present invention provides a method for sending data in a test system having a switch emulator and a network test device. The method includes first outputting from the switch emulator first network data on a first media independent interface based on a first interface clock, and outputting from the switch emulator a reference clock. The method also includes converting the first network data for reception by a second media independent interface of the network test device configured for receiving network data based on a second interface clock, and generating the first and second interface clocks based on the reference clock.
Another aspect of the present invention provides an apparatus. The apparatus includes a first inverted media independent interface configured for receiving first data, and supplying second data and a first interface clock, for a connected first media independent interface, and a second inverted media independent interface configured for receiving the second data, and supplying the first data and a second interface clock, for a connected second media independent interface. The apparatus also includes a clock generation circuit configured for generating the first interface clock and the second interface clock based on an external reference clock.
Still another aspect of the present invention provides a test system comprising a switch emulator, a test instrument, and an interface converter. The switch emulator has a first media independent interface configured for outputting first network data based on a first interface clock, the switch emulator outputting a reference clock. The test instrument has a second media independent interface configured for outputting second network data based on a second interface clock. The interface converter is configured for generating the first and second interface clocks based on the reference clock. The interface converter converts the first network data for reception by the second media independent interface, and the second network data for reception by the first media independent interface.
Additional advantages and novel features of the invention will be set forth in part in the description which follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The advantages of the present invention may be realized and attained by means of instrumentalities and combinations particularly pointed in the appended claims.